Ion implantation is a technique for introducing conductivity-altering impurities into a workpiece such as a wafer or other substrate. A desired impurity material is ionized in an ion source of an ion beam implanter, the ions are accelerated to form an ion beam of prescribed energy, and the ion beam is directed at the surface of the workpiece. The energetic ions in the beam penetrate into the bulk of the workpiece material and are embedded into the crystalline lattice of the workpiece material to form a region of desired conductivity.
Conventional ion beam implanters often include a number of extraction electrodes, including a suppression electrode and a ground electrode configured to extract an ion beam from an ion source and to manipulate (e.g., focus and/or direct) the ion beam in a desired manner. The extraction electrodes are commonly mounted on an electrode positioning system having a motorized, multi-axis gantry for facilitating selective movement of the extraction electrodes relative to the ion source. For example, if an ion beam is out of focus when the ion beam is initially extracted from the ion source, the gantry may reposition the extraction electrodes in a corrective manner to focus the ion beam properly. It is advantageous to perform such corrective focusing quickly and precisely in order to reduce processing times and to produce workpieces with good micro-uniformity.
Traditional electrode positioning systems such as the one described above are associated with a number of shortcomings. For example, motorized gantries employed in such systems may exhibit less than optimal response times and positional accuracy. Additionally, such systems are often very large, often with components extending outside of a vacuum sealed source chamber containing an ion source and extraction electrodes, therefore requiring large and complicated vacuum sealing arrangements. Still further, traditional electrode positioning systems are often very expensive, have significant axis coupling and motion profile limitations, and are difficult to modify.